This invention relates to the recovery of metals from low level aqueous sources by extraction. More particularly, it is concerned with a recyclable extration process for the recovery of tungsten from low level aqueous sources.
Tungsten is an important constituent of alloy-hardened metals and cutting tools, and is indispensable in the manufacture of electrical components such as heating elements and electric lamp filaments. The increasing scarcity and value of this vital metal require that efficient and economical means be found for the recovery of tungsten from sources which contain low levels of the metal.
Two important classes of low level sources of tungsten are naturally occurring alkaline brine solutions such as those of Searles Lake, Calif. and the effluents of hydrometallurgical plants which process tungsten-bearing ores. Searles Lake is estimated to contain approximately 170 million pounds of tungsten trioxide, but at brine concentrations of only 50-70 parts per million. Tungsten-bearing ore processing plant effluents likewise contain small but significant concentrations of tungsten, typically on the order of 50 parts per million.
A number of processes have been proposed for the recovery of tungsten from aqueous solutions, some based on the known tendency of tungsten to form complexes with a variety of chelating or complexing agents. Many of these processes are capable of efficient, often quantitative, recovery of tungsten in single-step extractions but are non-recyclable. Such processes have been applied to advantage in the analytical determination of tungsten or for small scale batch extractions of tungsten; however, single cycle extraction processes are not useful for the recovery of commercial quantities of tungsten from low level sources. The cost and waste disposal problems associated with the consumption of large amounts of reagent chemicals per pound of tungsten recovered prohibit the use of single cycle extraction processes for recovery of tungsten from such sources as Searles Lake brines.
The process in accordance with this invention provides a recyclable, efficient,, and economical method for recovery of tungsten from low level aqueous sources such as natural alkaline tungsten-containing brines and hydrometallurgical plant waste streams.